Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W=map(int,input().split())
S=[]
count=0
for _ in range (H):
    A=list(input())
    for a in A:
        if a=='.':
            count+=1
    S.append(A)
 
mas=deque([(0,0,0)])
while mas:
    y,x,n=mas.popleft()
    if 0<=y<=H-1 and 0<=x<=W-1:
        if S[y][x]=='.':
            S[y][x]=n
            mas.append((y+1,x,n+1))
            mas.append((y,x+1,n+1))
            mas.append((y-1,x,n+1))
            mas.append((y,x-1,n+1))
short=S[H-1][W-1]
if short=='.':
    print(-1)
else:
    print(count-(short+1))